Fitting a 916-style Steering Damper

By Banoffee.

My slabby has a lively front end, so I’ve been wanting to fit a steering damper for ages. I even acquired the period Daytona fitting kit and damper however couldn’t get that to work with my USD front end. So, seeing as I wasn’t keen on modifying the frame to take a bolt-on side mounted damper the only option left was a 916-style fitment. Seeing as I’m running an Ohlins rear shock, the damper had to be Ohlins to match of course!

Basic theory:
Whilst steering damper manufacturers don’t list fitting kits for oldskool bikes, it’s actually a simple matter of taking the measurements and then doing some research to find a suitable kit (or parts from several kits).

The measurements: (Note – some measurements are taken with internal vernier edges, some external. These are just shown to illustrate, you should of course check your own measurements carefully!)

A: Yoke nut centre to tank front mount centre

AB: Top of tank mount to top of top yoke

BC: Between centre of tank front mount bolts

CD: Between LH lock and centre (then multiplied by 2)

DThe research:
I took a tape measure with me to bike meets, bike shops etc to measure up more modern bikes (with owners permissions of course when they were about!) and also bothered a few people selling kits on ‘that auction site’.

My bike:
(750G with 400gk76a USD front end)
A: approx 50mm
B: approx 60mm
C: approx 50mm
D: approx 60mm

Things to note:
On my slabby, the damper is quite close (5-10mm) to the tank. Double, triple check all measurements to ensure it won’t foul anwwhere.
Source the fitting kit before buying a damper so that you can mock up and modify if necessary. Setting a good search on ‘that auction site’ makes this surprisingly easy and cost-effective.
For the damper stroke, obviously err on the side of slightly longer but not too long as it will look unbalanced.

The result:
I picked up a 2000-model H*nda Firebl*de Harris fitting kit from ‘that auction site’ for a whopping �20. Measurements were near-perfect as a 1-2mm on the tank mount, etc. is just fine. Only slight drawback was 30mm lower ‘B measurement’ so I acquired a 30mm tubular spacer.

EMy ‘D measurement’ (remember to multiply by 2 of course!) meant an approx 60mm stroke damper so I ordered a 63mm stroke Ohlins damper from BikeStuff (cheers Rich!).
In the pics below you can see the finished result. I’ve lost a tiny amount of right-lock, however, eventually I’ll get a spacer made up to under the tank-mount part which will solve that. All-in-all I’m well pleased!


Journey to the center of Mikuni’s BST38SS carbs

Journey to the center of Mikuni’s BST38SS carbs.

When I was studying my new 38mm slingshot carbs my eyes fell on the small rubber hose which runs along the outside of the carbs from the float chamber to somewhere above the intake. I disconnected the hose and started tracing the circuit inside the carb.I did this by reconnecting the hose to one of the fittings and bowing into it. So by hearing where the air escapes you know the routing of the circuit.bst38ss-1

The top fitting connects to the uppermost hole in the bellmouth, but when I blew into the fitting of the float chamber I seemed to have hit a dead end because there wasn’t any air escaping. I noticed a small plug which looked like a jet inside the float chamber. I removed it and now I could blow trough it. First I thought the jet had been clogged but after closer inspection it really was a plug instead of a jet. So there was a hole in the bellmouth that connected to the float chamber, but the hole was plugged. I had some sleepless nights trying to figure out what the function of this would be.bst38ss-2

Then I decided to do some investigation on the web. I didn’t expect to find much info on Mikuni carbs on the web, but suddenly I found this article deeply hidden inside Factory Pro’s website…

Power Jet Circuit, GSXR750, as installed on air cooled gsxr750 w/ 38mm Mikuni carbs, 90-92

Power jet carbs – Mikuni’s great addition to a carb used in a high rpm application.

The power jet adjusts high rpm mixture, in the gsxr750 – from 10 to redline, in 1/3rd the step of a main jet change. Changing a main jet, in the 38mm carb, as installed on the gsxr750, adds or subtracts up to 2% CO per main jet change – when the CO% needs to be adjusted in in .2%-.4% for best power attainment.
Changing the power jet allowed much finer increments of change and, just as critically, happened to change the fuel delivery curve to what was optimum for the gsxr750 – something that would have required main air jet changes and other modifications to attain, but would still leave the main jet fuel delivery steps too coarse.
Strange. This Powerjet circuit works wonderfully when tuned on the stock airboxed gsxr750 (and it’s pretty straightforward to tune on our EC997 Low Inertia Eddy Current dynamometers unlike simple inertia dynos.

The method of operation is as follows.
At full throttle, as the rpm increases, at exactly 10k, there is enough of a pressure differential between the float bowl and the airbox interior to draw fuel up the black hose on the LH side of the carb and exiting through the hole at the top of the bellmouth of the carb.
The fuel is metered by a jet that is located in the bottom of the float bowl. The jets are sized in increments of 2.5 or .025mm. Usual size for a gsxr750 with a stock airbox and air filter might be between #58 to #67.5.
The power jet circuit, when properly tuned, adds the equivalent of 2-3- main jet sizes “on top” of the main jet, so, if you were not using the power jet circuit, i.e. had a “0” or blanked jet installed with a #125 main jet, you would use a #117.5 with a #62.5 power jet installed.

Since this particular circuit works on the pressure difference between the float bowl and the airbox interior, it is absolutely affected by any change in the pressure differential. If the air filter is changed to less restrictive unit or the airbox inlet is modified, creating less restriction – the power jet area (size) should have to be increased above the usual size, though, a BMC or K&N, as installed for stock replacement, may only require 1-2 sizes increase in the power jet (in addition to +2-+3 on the main jet circuit).

If the airbox is removed, there is no longer a sufficient pressure differential to pull the fuel up the ~2.5″ vertical rise from the float bowl to the outlet in the bellmouth and the circuit is no longer effective.

Why is the Powerjet circuit difficult to tune on a simple inertia dyno and easy on our EC997 Low Inertia dynamometer? According to the former owner of Dynojet, the powerjet circuit simply doesn’t work because there is a lag in fuel delivery at 9.5k rpm – creating a flat spot there. It turns out that the reason that he saw that is that the dynojet dyno has insufficient load to simulate the Real World Loading ™ that is present on the bike in 4th and higher gears on the road or track. There is a slight delay in the onset of Powerjet fuel delivery, but it’s only vaguely present in second gear in the real world, and not present in higher gears due to the slower acceleration rate that occurs when you are actually riding. If you were racing, as Yoshimura USA and other non sponsored, large US Suzuki sponsored teams (we lent them carbs for the Finals) verified, the kit outperformed anything dynojet had to offer.

How to tune:
1. Install the main jet that produces the best power at full throttle / 8k-9k.
2. Install the powerjet set that produces the best power at full throttle / 10k to redline.
3. Raise or lower fuel level to get best power at full throttle / 3k.
4. Recheck main jet and needle height if you needed to lower the fuel appreciably.
5. Adjust fuel screws for best idle.
Note – this is the “short” tuning list!

The size of the main jet DOES affect the low and midrange. Excess leanness isn’t usually the problem on these carbs. Using a #117.5 vs. a #122.5 main jet (PJ equipped vs. using a #0 PJ ) leans and crispens the lowend and midrange for better off idle and corner exit performance.

There other applications on other motorcycles that use circuits that are called “power jet” circuits that work on different principles – some are electronically controlled and work in the midrange like RGV250, the RS250 for upper topend, where they activate and deactivate through different ranges and still others work for different reasons and by different principles.
“Power Jet” is a catchy sounding name and it gets used every few years or so…

Why did Suzuki specify that US and UK models, for example would have a blank or “0” jet installed, disabling the circuit and other countries, like Canada, got the activated power jet circuit (though with pretty odd settings)?
Emissions? I don’t think so. With the basic fuel level and needle settings virtually the same on both applications, using the larger main jet, as required with the circuit blanked, would only increase hydrocarbon emissions under measured conditions.

At any rate, the circuit works extremely well in dealing with the coarse main jet metering steps of the older style gsxr750 carbs – 1st through 5th place at the 1990 WERA Grand National Finals used our Factory Pro #CRB-S06-1.0 Carb Recalibration Kit. Pervasive kit use followed for the next couple of years -until 1992, the last year of the power jet.


Says it al really, but what I can’t figure out is why mine have size 0 jets fitted as my carbs came from the UK and so should have a functional circuit according to the article.
But anyway, as I am using separate K&N’s the powerjet circuit won’t be able to function properly so I removed the tubes and plugged the outlets inside the bellmouths.
This way you won’t have to disconnect the tube every time you want to change the main jets which can save you a lot of dyno time and therefore money. Now you only have two screws for the top cap and two for the float chamber which makes them very service friendly.

Thanks to Factory Pro for restoring my good night sleep!

Now that we are talking carburation technology I would like to point out two other things that are important.

When I remove the airbox and fitted separate K&N’s there were a few hose fittings that I didn’t know what to do with.bst38ss-4 In the middle of the bank of carbs there’s a 14mm big hole which acts as a breather for the float chambers. You need to connect a hose to this which is about 30 centimeters long to

A.) prevent dirt from entering the float chambers, maybe you’d even fit a small filter to the other and of the hose. A good and cheap trick is to nick some of your girlfriend’s nylons, put a piece of it at the end of the hose and keep it in place with a tie-rap.
B.) create a kind of buffer for the air pressure below the diaphragms. This is very important for the same reason you need to add tubes to the fittings of the float chamber breathers.

You need to connect a tube about 20 centimeters long to the fittings bst38ss-3of the float chamber breathers which are located between carbs 1&2 and 3&4. If you don’t do that the air pressure inside the float chambers will become very perceptive to pressure changes outside the carb like when you get some sudden sidewind or pass a big lorry.
I didn’t believe this at first until a dyno operator did a run before- and after fitting the hoses. The hoses made the powercurve much smoother and therefore made it easier to choose the right jetting.

Marc Salvisberg from Factory Pro Tuning says;

In the US, with a stock airbox, we didn’t have ANY problems with crosswinds, even 40-50mph gusting crosswinds at full lean at 100mph boogie. Actually, there is one problem – getting broadsided with a 50mph gust WILL push you off the track! Willow Springs in southern California. I thing that the biggest problem was the carb tuning as rides with our carburetion setups could: run with or without float bowl tubes, tuck their knee in of out, draft to the inside or outside of another rider while in a strong crosswind! It’s been a few years, but I definitely do remember the lack of problems with crosswinds. Urban myths started by someone in the States! Do the hoses affect the carburetion? Perhaps, to a very small effect. Less than running the bike again and increasing the crankcase temp 10F!

The only thing I can say is that we did a run with- and without the tubes installed and the effect was very clearly visible on the dyno graph. So when you fit separate K&N filters be sure to fit those hoses for the horses!

Thanks to Sandro Serafini, creator of Evo2 for the delicious carbs.

Frankenstein’s guide to oil cooled engines

Before anything, I would like to have it said that I wrote this in my best knowledge and do
not want to be held responsible for any mistakes. I’m confident about what I’ve seen and done,
but since I’m not the only one messing around with gixxers, I can hardly ever be sure that
the engine I find in a 89 1100R is really an 89 1100R. I’ve left the types before 88 out,
since I have not much experience with them.

There are mainly 2 types of 750’s, the 88-89 short stroke, and the pre-88 and 90-91 long stroke.
(The 750F is basicly the same motor as the 88-89 short stroke, the B6 and GSXF600 are basicly
the same as 90 long stroke with a smaller bore).
1100R motors from 88-92 are similar to the 1100F and B12 motors. The 1100G is also similar,
but has an axle drive. They all have the same stroke, and only the B12 has a 1mm bigger bore.

Apart from the color, all the GSXR, GSXF, GSXG and Bandit ignition covers are the same (except
the 750RK).

The clutch covers are depending on the clutch operation, there are 3 possibilities:
(The dry clutch is left out, to avoid making it more confusing).
1.The GSXF600, GSXF750 and B6 have the clutch cable connected to a mechanism on the sprocket
cover, and the clutch is operated by a push pin through the primary gear box shaft.
2.The 750R has the clutch mechanism in the clutch cover (on the right side). The 88-89 clutch
cover is recognizable by a smooth clutch cover, the 90-91 has a bubble in the center. They are
very similar, but since the engines have a different clutch, I don’t think these covers can be
swapped, I haven’t tried though.
3.The 1127’s and B12 all have the clutch mechanism on the sprocket cover, like the 600’s and
the 750F, but then hydraulically operated. The mechanisms on the sprocket cover can all be
swapped, so it’s possible to put a cable operation from a B6, F6 or F750 on an 1127 (and v.v.),
although it might need some adjustment of the length of the pushrod.
This also means that, since the clutch covers on the 600’s, 750F and 1127’s are nothing but
covers, they can be swapped.

The startermotor covers from the 1127’s are all the same (The startermotor covers from the 1052
engines are not the same) The 1127 covers can be recognized by a kind of bubble, to accomodate
the bigger starter motor. The 600′ and 750’s have a smaller starter motor, and the top line of
these covers is straight. (I believe the 1052 motors also have this smaller starter motor and
cover). Covers can be swapped among the 600’s and 750’s, but an 1127 cover only fits an 1127.

The oil pan on all 1127’s are the same, but the B12 is different. The 750F and 750R 88-89 have
the same oil pan as the 1127’s. The 91-750R and B6 have a similar or same oil pan as the B12,
I’m not sure. However, it is possible to swap these oil pans, as long is you change the oil
pickup as well. Oil hoses on the 1127 pans connect at the front, the others at the bottom.

The valve covers are different depending on the cam chain type, and the cylinder head size.
The B6 cover only fits the B6, the B12 cover only fits the B12. The 750R-90 and 91 covers
are the same. All the 1127 and the 750R-88/89 cam covers are the same.

There a 3 main items which make the difference in crankshafts.
1. Stroke
2. Clutch gear
3. Camchain type

1. The 1127’s and B12 all have the same stroke. The 600’s and 90-91 750R’s have the same
stroke. The 88-89 750’s and the 750F have the same stroke.
The stroke is important because this directly reflects on the number on teeth on the
clutch gear (ie. the gear diameter).
2. All GSXR1127 crankshafts are the same. The GSXF and G have a helical
cut gear, so when using a GSXF1127 crank You will have to use a GSXF1127 clutch basket as well.
3. All GSXR’s (both 750 and 1127) have the same type camchain, but the B6 and B12 are
different. Since the cam chain is driven from the crankshaft, this means these crankshafts
are not interchangeable with GSXR crankshafts, unless you also change the cam chain, tensioner,
guides, cam sprockets, cam covers, cam guiding between cam shafts.

All the 3 items above have to match. Swapping a crankshaft with a type that has the same
stroke, clutch gear and cam chain is no problem. If you start mixing, you have to match
clutch to the crankshaft (and in some cases gearbox), or cam chain stuff to the crankshaft.

Connecting rods from B6, 750R-90 and 750R-91 can be swapped. 1127 rods are all the same.
I have used B12 rods in 1127’s; I found there was a minor weight difference, but they could
easily be matched. This difference might have been incidental.

I left out the dry clutches on purpose, since I have no experience with them.

The GSXR1127 89-on and B12 have a diaphragm spring, the GSXF/G have normal springs.
The GSXR and B12 have a straight cut gear, the GSXF/G have a helical cut gear.
Because of the different gear on the clutch basket, the clutch basket is not swappable.
Since the types with a diaphragm spring have a longer shaft to accommodate the bolt for the
central spring, these parts are also not swappable. It is possible to use the internal clutch
parts from a ‘normal spring type’ in the basket (or actually on the gear box shaft) from a
‘diaphragm spring type’, but you need to fill the space on the longer shaft. It is not
possible to use the diaphragm style clutch on a GSXF gear box shaft, since the shaft is to short.

The 88-89 750R have a large (actually the largest) diameter but relatively flat clutch.
Although the gear box shaft is the same, the 88-89 clutch can not be swapped with the 91
clutch because the crankshaft diameter (and consequently tooth count) is different.
Although the B6 clutch is the same diameter as the 91 750R clutch (since they have the
same stroke), there is not a lot to swap there since the plates are different and the
gear box shaft are differently machined.

Cylinders block with pistons from 1127’s can all be swapped. B12 block+pistons fit the 1127
as well, or only pistons+have your 1127 block bored.
88-89 750’s is same as GSXF750.
B6 and 90/91 750R have 18mm wrist pins, whereas 88-89 750R, GSXF750, 1127’s and B12 have
20mm pins.
Since the B6 and later 750R 90-91 have the same stroke, cylinder block dimension, and wrist pin
diameter, the 90/91 block+pistons can be swapped with the B6 stuff (although you’ll have to
check that the pistons don’t hit the head/valves).

The long stroke engines (ie. B6, GSXF600, 90/91 750R) have the same dimensions, just the
combustion chamber and valves in the 750’s is bigger. So somebody who want less power could
fit a B6 top on a 90 750R. Camshaft type on the B6, GSXF600 and 90 750R is forked rocker,
meaning 1 cam for each pair of valves. 91 750R has shim type with 1 cam for each valve.
If swapping the camshafts as well, the 90 and 91 heads can be interchanged.
Both the 90 and 91 750R top ends can be used on a B6, but since the B6 has another type of
camchain, it is needed to maintain the B6 cam chain tensioner, guides, cam sprockets, valve
cover etc.

The 750 short stroke engines 88/89 heads have the same outside dimensions as the 1127/B12,
but the combustion chamber is smaller (although the valves are the same diameter).
The 1127R-91/92 has the same style head as the 750R-91, but
not much to swap; 1100 valve spacing differs (so camshafts can not be swapped), 1100 valves
are bigger, outside head dimensions differ.
As mentioned, 750R-88/89 valves are the same as 1127/B12, exception are the 1127R-91/92 valves.
These heads have shim type adjustment, and therefore different cams and longer valves.

It is possible to modify a 1127 shim head to a forked rocker head. It’s quite some work, and
you’ll need the valves from the forked rocker head, the rockers, cam shafts. You’ll need to
make all the spacers yourself, or in fact I believe there is a company that has or used to
have a modification kit.

Cam shafts from the 1127F, 750F, 90-750R, B6, B12, 88/89 750R are theoretically all swappable,
but of course the profiles are different. The long stroke 750’s have a different tooth count
on the cam sprockets so they can not be mixed. B12 sprockets can only be used in the B12.
B6 sprockets can only be used in the B6. 1127F and 1127R sprockets are the same, 88/89-750R
sprockets are similar, but the timing marks are different. (Meaning they can only be used if
slotted and timed)

1127: Depending on the clutch type there are long and short shafts. Also the gears themsleves
from these boxes are different. It may be possible to swap a few gears between these boxes,
but the gearchanges might not be very smooth.
Apart from the clutch type, the 91-92 1127R has a double row bearing on the output shaft, and
therefore a slightly different crankcase (around the bearing area).

Gear boxes from all 750’s are swapable. I have no experience with swapping gears seperately.

The B6 has a different shaft, so it can only be used with it’s own clutch.

Although it might seem there are so many differences, a lot can be mixed, as long as the right
parts are choosen, a few examples.
(There are some basic guidelines to assemble an engine, like check compression, cam timing, valve
clearance etc., no matter what combo you’re making).

1. A 1052 crank fits in 88-89 750R and 750F cases, but a 1127 crank doesn’t (but the cases can
be modified to take the 1127 crank as well)

2. A 750R-90 or 750R-91 top end on a B6.
It’s actually very easy, and I think all the info you need is above. Both engines have the same
stroke, same wrist pin diameter. Theoretically, it would be possible to put only 750 cylinders
and pistons on a B6. However, the pistons are designed to fit the 750 head and since that also
fits, why not install a 750 head as well (with bigger valves). Since the B6 has another cam chain
the B6 cam chain tensioner, cam sprockets, cam chain guides and B6 valve cover need to be
used. Then there are 2 options: either go for a 750R-90 top end, which uses forked rockers
like the B6 does (so it’s possible to use either the B6 cams or the 750R cams), or go for a
750R-91 top end, which uses another type of rockers so it is not possible to keep the B6 camshafts.

3. A 750R-88/89 top end on a 750R 90/91 bottom end (or 86-87 bottom).
This is a bit more difficult, since it needs some more work and imagination then the plain
assembling of a B6/750.
The 750R-88/89 have a bigger bore, so the idea of this combo is to increase the capacity of the
engine. (You could also take this combo the ‘other way around’, and fit a 90/91 crankshaft + clutch
in a 88/89 engine.)
Since the dimensions of the heads are not the same, it is not possible to only put the 88/89 pistons
+cylinders on the 90/91; the head of the 90/91 would not fit the cylinder block. So the complete
88/89 top has to be installed on the 90/91. The wrist pins on the 90/91 are 18mm, on the 88/89 20mm,
so the small end of the 90/91 rods have to be bored to 20mm. Now the whole thing could mechanically be
assembled, but since the stroke of the 88/89 is smaller, the height of the cylinder block is smaller.
This has to be compensated by putting a spacer under the cylinderblock. (This spacer would very
roughly have to be 1/2 x the difference in stroke, but the only right way is to measure/calculate the

4. 750R 6 box in a 1127 motor
The only hard thing here is to have a hole drilled through the gear box shaft, for the pushrod.
The 750 6 boxes have a single row bearing on the output shaft, and the clutch does
not have a diaphragm spring. So the easiest 1127 engines to put a 6 box in are the ones with a
single row bearing on the output shaft, and no diaphragm clutch, ie. only the GSXF1127 engines.
In these engines the 6 box drops straight in, only the shaft has to be drilled.
Second easy would be an 1127R engine with a diaphragm clutch, but no double row bearing (88-90).
In this case the box would still drop in, but for the clutch one would have to use the inner
clutch parts from a GSXF1127 (with normal springs) and the outer clutch basket from the 1127R
(with a straight cut gear, not helical).
Most work is in a 91/92 1127R where one would have to match the clutch as above + find a
solution for the double row bearing (the solution is actually to turn the double row bearing
inside out, and make a little hole for the small pin).
Of course the shift drum and forks from the 6 box have to be used as well, but they drop in
any 1127 without problems.

5. 88-89 750R head or 750F head on a 1127 or B12
These heads fit as they are, and give higher compression, better ports, larger squish.
In the case of the 91-92 1127R you’ll need to use the 750 camshafts as well, since the
91-92 1127R uses shim type camshafts and the 750 head is forked rocker type. If you use the
91-92 1127R cam shaft sprockets they can be timed as in the manual.
In the B12’s case you could use the B12 or the 750 cams (although they have different profiles)
but will have to use the B12 cam shaft sprockets because of the different cam chain.
In the case of the 88-90 1127R you can use the 750 or 1127 cams, and use the 1127 cam sprockets
(timing ‘by the book’) or use 750 cam sprockets (timing to be done by yourself)


Alternator overcharging problems, oil-cooled engines

Alternator overcharging problems.

Right then ive got to the bottom of this problem and i bet most oil coolers have got this problem thanks to stuart who is a very clever electrical engineer/design.

Suzuki have tried to be clever using a closed loop design which may work when everthing is new perhaps.

Out of alternator are two leads the main power to battery and the other is the ignition feed to alternator which is trigger to turn reg on.
Problem here is voltage drop on the trigger wire, ive measured half volt purely at ignition switch, suppose age takes its toll. ive got further .3 volt loss through wiring and joints i can tell you the connectors are clean and look good.
So alternator battery lead reads say 12.6 volts (engine off) ignition lead reads 12.5 volts but lights on this drops to 11.5 volts where the battery lead reads 12.3 a drop of .8 through switch and harness, so when running when lights are turned on alternator compensator by ramping up output to 15.4 volts which cooks the battery.

Remove ignition feed wire to the alernator and use it to power a relay (switch side) the ignition wire out of alternator straight to positive on battery via the new relay.
Result constant 14.3 volts depending on battery state no matter whats on or off, result.

You have to connect via a relay as the reg would drain the battery in no time as this is trigger to turn reg side of circuit on as its a basic deign not like car 1 wire systems where the actual rotation of alternator triggers it on.

In the past ive destoyed batteries for no reason luckily the powerful little gel battery has lasted 3 years but at least now know the reason why, this has got to affect a lot of bikes this sort of age pointing bto reg when actually its working correctly.
Hope this is of i must also do a right up on cvs and good design change, to stop emulsion tubes wearing out.

Ignition wire from alternator ( to work out which of two wire this is it will be the wire that only has 12 volts on it when ignition is turned on, ie black wire on multi meter to earth red on meter prod each of cables in back of plug)

Cut this wire, the one coming from alternator now connect to positive on battery via a relay.
The other side of cut ignition wire coming out of loom connects to the switch side of this new relay obviously the other side of switch side goes to earth.
So when ignition is off relay is open so connection of battery to ignition wire on alternator and visa versa.

Just one thing: first i tried with a cheap relay, it had a difference of 0,2V on the switched wires, so it charged 14,7V. Then I got a better relay (no difference measurable) and it charges perfectly.